In conveying heated or cooled air from a furnace or an air conditioner, the air is usually conducted to a rectangular cross-section main duct and thereafter through branch ducts that extend from the main duct. In recent years, these branch ducts have been formed from sealed circular cross-section sheet metal pipe. These branch ducts then carry the conditioned air to registers that open into rooms in the building to permit circulation of the conditioned air within the rooms.
The transition of air from the main duct to the branch duct has not been very efficient because the branch ducts usually extend at right angles to the main duct causing turbulence in the air as it transfers. Further, the type of fittings used previously has required extensive sealing to prevent leakage of air through the joints. Newer building codes now require that there be minimal leakage in the heating and air conditioning systems.
The fitting of the present invention increases both the efficiency of the flow of air through the system and the ease of assembly of the system as will be seen as the description proceeds in conjunction with the attached drawings and the appended claims.